The invention relates to a trunk holding ring according to the preamble of the claim 1.
Young, freshly planted trees are supported by means of tree stands during approximately the first ten years of their growth. Tree stands are structural groups which posses tree stakes surrounding the tree, the upper ends of which are connected by means of tree holding rings, which serve at the same time for supporting the tree trunk during the growth.
In order to adapt the tree holding rings to the diameter increase of the growing tree, these are formed as three-part clamps, as the German Utility Model Specifications Nos. 80 25 171 and 82 12 913 describe it. From the known clamp segments stake holders are extended outwards. These are connected by way of stake forks to the tree stakes dug in around about the trees. The clamp segments, padded inside for the protection of the tree, are connected at their ends by tangential screws.
Even the assembly of a tree stand of this type is complicated and time-consuming. The clamp has to be screwed together by means of the tangential screws at the height determined by the tree stakes. At the same time a certain play has to be established between tree trunk and clamp. This demands craft skill. Moreover, the stake holders have to be placed on threaded rods extending radially outwards. The former are then pressed against the tree stakes and fastened to them by means of lock nuts. A compensation of a naturally occurring eccentric position of the tree relative to these tree stands, generally present, is, if not impossible, uncommonly difficult.
For adapting the clamp diameter to the increasing thickness of the growing tree, the clamp circumference has to be enlarged by twisting the tangential screws on the clamp segments. This is complicated because at the same time the clamp segments have to be rearranged symmetrically and centred to the tree, for the proper support of it. For this, experience and craft skill are demanded. In principle, an alternation of the clamp's circumference has to be undertaken at certain intervals of time.
Owing to such an increase of circumference, the distance between the clamp and the stationary tree stakes is also shortened. In this way, the adjustment of the individual clamp segments is made more difficult due to the reactive forces arising. These momentary loosening or damaging forces are transmitted to the ends of the tree stakes. The procedure with these clamps cannot be left to inexperienced trainee personnel.
In the transportation of older trees of considerable size with a weight of up to 6 tonnes, these are transported by means of a gripping apparatus, as the German Auslegeschrift DE-AS No. 11 75 933 describes. With this gripping apparatus, these older and heavier trees are lifted out of the soil together with the dug out root balls. The transportation to the new planting location takes place in this gripping apparatus.
This known gripping apparatus possesses two concentric, cylindrical pairs of half hoops. The inner pair is rotatably mounted in the outer. Both pairs of half hoops are placed around the tree to be lifted out, and then closed. The inner pair of half hoops carries a spindle with pressure disc. By means of this spindle, the pressure disc is so actuated that a tree trunk is firmly clamped in, between this (disc) and the inner wall of a hoop. The clamping in must be so firm that at least half the lifting forces arising in connection with the lifting out of the heavy tree can be transmitted to this clamping point.
The known hoops are not formed as circular, but are cylinder sections. An apparatus of this type, exerting great clamping forces on a tree trunk, is totally unsuitable for a support of a young, growing tree, to be carried out with play. This known clamping technique cannot suggest any solutions of the problems which arise in connection with the supporting of young growing trees.